Balanced microdevice

ABSTRACT

A balanced microdevice comprising a substrate, a movable structure overlying the substrate, an element and a lever assembly having a pivot and a lever coupled to and pivotable about the pivot. The lever has a first extremity coupled to the movable structure and an opposite second extremity coupled to the element. The movable structure causes the lever to pivot about the pivot so as to move the element in a direction of travel. The element is substantially mechanically balanced to inhibit undesirable movement of the element in the direction of travel in response to externally applied forces.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional patent applicationSer. No. 60/323,628 filed Sep. 19, 2001 and is a continuation-in-part ofU.S. patent application Ser. No. 09/727,794 filed Nov. 29, 2000, nowU.S. Pat. No. 6,469,415, which claims priority to U.S. provisionalpatent application Ser. No. 60/167,951 filed Nov. 29, 1999; U.S.provisional patent application Ser. No. 60/174,562 filed Jan. 5, 2000;U.S. provisional patent application Ser. No. 60/227,933 filed Aug. 25,2000 and U.S. provisional patent application Ser. No. 60/234,042 filedSep. 20, 2000, the entire contents of each of which are incorporatedherein by this reference.

FIELD OF THE INVENTION

The present invention is applicable to the field of microdevices and ismore specifically applicable to electrostatic microdevices.

BACKGROUND

Microactuators, and particularly electrostatic microactuators, haveheretofore been provided. See, for example, U.S. Pat. No. 5,998,906 andInternational Publication Number WO 00/36740. Such microactuators can beutilized in microdevices, for example in the telecommunications industryand in the data storage industry, for moving optical elements. See, forexample, International Publication Number WO 00/36447 and U.S. Pat. No.6,134,207. It has been found that applied external accelerations canundesirably effect the performance of microdevices employingmicroactuators.

What is needed, therefore, is a microdevice that is substantiallymechanically balanced such that an element moved thereby does notappreciably move when subjected to external accelerations.

What is also needed is a rotary electrostatic microactuator that rotatesabout a pivot point disposed outside the confines of the microactuator.

SUMMARY OF THE INVENTION

In general, a balanced microdevice is provided that includes a substrateand at least one comb drive assembly having first and second comb drivemembers. The first comb drive member is mounted on the substrate and thesecond comb drive member overlies the substrate. At least one springmember is provided that has a first end portion coupled to the substrateand a second end portion coupled to the second comb drive member. Thefirst comb drive member has a plurality of spaced-apart first comb drivefingers and the second comb drive member has a plurality of spaced-apartsecond comb drive fingers. The second comb drive member is movablebetween a first position in which the first and second comb drivefingers are not substantially fully interdigitated and a second positionin which the first and second comb drive fingers are substantially fullyinterdigitated. A counterbalance is carried by the substrate and coupledto the second comb drive member for inhibiting undesirable movement ofthe second comb drive member in response to externally appliedaccelerations to the microdevice.

In one embodiment, a microdevice is provided that includes a substrate,a movable structure overlying the substrate, an element and a leverassembly having a pivot and a lever coupled to and pivotable about thepivot. The lever has a first extremity coupled to the movable structureand an opposite second extremity coupled to the element. The movablestructure causes the lever to pivot about the pivot so as to move theelement in a direction of travel. The element is substantiallymechanically balanced to inhibit undesirable movement of the element inthe direction of travel in response to externally applied forces.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are somewhat schematic in manyinstances and are incorporated in and form a part of this specification,illustrate several embodiments of the invention and, together with thedescription, serve to explain the principles of the invention.

FIG. 1 is a plan view of an electrostatic microactuator.

FIG. 2 is a plan view of a balanced microdevice of the present inventionutilizing an electrostatic microactuator.

FIG. 3 is a fragmentary plan view of a portion of the firstmicroactuator of the balanced microdevice of FIG. 2 taken along the line3—3 of FIG. 2 and rotated 90°.

FIG. 4 is a cross-sectional view of the first microactuator of FIG. 2taken along the line 4—4 of FIG. 2.

FIG. 5 is a fragmentary plan view of the first microactuator of FIG. 2taken along the line 5—5 of FIG. 2 and rotated 90°.

FIG. 6 is a plan view of the balanced microdevice of FIG. 2 in a secondposition.

FIG. 7 is a fragmentary plan view, similar to FIG. 3, of a portion ofthe first microactuator of FIG. 6 taken along the line 7—7 of FIG. 6 androtated 90°.

FIG. 8 is a fragmentary plan view, similar to FIG. 5, of the firstmicroactuator of FIG. 2 in a position between the position of FIG. 2 andthe position of FIG. 6.

FIG. 9 is a plan view of another embodiment of the balanced microdeviceof the present invention.

FIG. 10 is a plan view of the balanced microdevice of FIG. 9 in a secondposition.

FIG. 11 is a plan view of a further embodiment of the balancedmicrodevice of the present invention.

FIG. 12 is a plan view of the balanced microdevice of FIG. 11 in asecond position.

FIG. 13 is a plan view of a microdevice with lever assembly of thepresent invention.

FIG. 14 is a plan view of the microdevice with lever assembly of FIG. 13in a second position.

DETAILED DESCRIPTION OF THE INVENTION

In general, microactuator or motor 507 shown in FIG. 1 is a MEMS-basedmicroactuator capable of being used in a microdevice such as tunablelaser of the type disclosed in copending U.S. patent application Ser.No. 09/728,212 filed Nov. 29, 2000, the entire content of which isincorporated herein by this reference. Microactuator 507 is a of arotary or angular electrostatic microactuator formed from a substrate526 that extends substantially in a plane. A plurality of first andsecond comb drive assemblies 527 and 528 are carried by substantiallyplanar substrate 526 and are arranged on the substrate in first andsecond sets 531 and 532. Each of the first and second comb driveassemblies includes a first comb drive member or comb drive 533 mountedon substrate 526 and a second comb drive member or comb drive 534overlying the substrate 526. At least first and second spaced-apartsuspension members or spring members are included in microactuator 507for supporting or suspending second comb drives 534 over the substrate526 and for providing radial stiffness to the movable second comb drives534. As shown, first and second outer suspension members or springs 536and 537 and a central suspension member or spring 538 are provided.Second comb drives 534 are part of a movable structure 539 overlying thesubstrate 526. Any suitable movable element such as an optical element506 can be mounted on movable structure 539 for movement relative tosubstrate 526. The optical element 506, as shown in FIG. 1, is amicroreflector.

Substrate 526 is made from any suitable material such as silicon and ispreferably formed from a silicon wafer having a thickness ranging from400 to 600 microns and preferably approximately 400 microns. Springs536-537, first and second comb drive assemblies 527 and 528 and theremainder of movable structure 539 are formed atop the substrate 526 bya second or top layer 542 made from a wafer of any suitable materialsuch as silicon. Top layer or wafer 542 has a thickness ranging from 10to 200 microns and preferably approximately 85 microns and is preferablyfusion bonded to the substrate 526 by means of a silicon dioxide layer(not shown). The components of microactuator 507 are preferably etchedfrom wafer 542 by deep reactive ion etching (DRIE) techniques or theLithographie Gavanometrie and Abformung (LIGA) process, which permitsuch structures to have a high aspect ratio and thus enhance theout-of-plane stiffness of such structures. Springs 536-538 and movablestructure 539 are spaced above the substrate 526 by an air gap (notshown), that ranges from 3 to 30 microns and preferably approximately 15microns so as to be electrically isolated from the substrate 526.

First and second sets 531 and 532 of comb drive assemblies aresymmetrically disposed about a radial centerline 543 of microactuator507 and each include a first comb drive assembly 527 and a second combdrive assembly 528. Second comb drive assembly 528 of the first set 531is disposed adjacent centerline 543 and first second comb drive assembly527 of the second set 532 is disposed adjacent the centerline 543. Afirst comb drive assembly 527 is spaced farthest from centerline 543 inthe first set 531 and a second comb drive assembly 528 is spacedfarthest from the centerline in the second set 532. Each of the combdrive assemblies 527 and 528 is centered along a radial line whichintersects radial centerline 543 at the virtual pivot point (not shown)of microactuator 507. Each of the first and second comb drive assemblies527 and 528 has a length ranging from 300 to 3000 microns and preferablyapproximately 1300 microns, and commences a radial distance from thepivot point of microactuator 507 ranging from 500 to 5000 microns andpreferably approximately 2000 microns.

First comb drive 533 of each of first and second comb drive assemblies527 and 528 is immovably secured to substrate 526. Each comb drive 533has a radially-extending bar or truss 546 provided with a first or innerradial portion 546 a and a second or outer radial portion 546 b. Aplurality of comb drive fingers 547 extend from one side of bar 546 inradially spaced-apart positions along the length of the bar. Comb drivefingers or comb fingers 547 can be of any suitable shape and arepreferably approximately arcuate in shape. Comb fingers 547 extendperpendicularly from bar 546 and thereafter substantially arc along aradius that preferably commences at the axis of rotation or virtualpivot point of microactuator 507. In a preferred embodiment, piecewiselinear segments are used to form the comb fingers 547 for approximatingsuch an arcuate shape.

Second comb drives 534 are spaced above substrate 526 so as to bemovable relative to the substrate and first comb drives 533. The secondcomb drives 534 have a construction similar to first comb drives 533and, more specifically, are formed with a radially-extending bar ortruss 551 having a first or inner radial portion 551 a and a second orouter radial portion 551 b. A plurality of comb drive fingers or combfingers 552 extend from one side of bar 551 in radially spaced-apartpositions along the length of the bar 551. Comb fingers 552 aresubstantially similar in construction and size to comb fingers 547 ofthe related comb drive assembly 527 or 528. Movable comb fingers 552 ofeach second comb drive 534 are offset relative to the respectivestationary comb fingers 547 so that comb fingers 552 can interdigitatewith comb fingers 547 when the second comb drive 534 is pivoted aboutthe virtual pivot point or pivot point of microactuator 507 towards therespective first comb drive 533.

The inner radial portions 551 a of the two second comb drive bars 551 ain each of the first and second sets 531 and 532 of comb driveassemblies are rigidly interconnected by a connector bar or beam 553that extends radially inside the respective first comb drives 533 ofsuch set 531 or 532. The outer radial portions 551 b of second combdrive assembly 528 in first set 531 and of first comb drive assembly 527in second set 532 are rigidly interconnected so that the second combdrives 534 in microactuator 507 move in unison about the pivot point ofsuch microactuator. Movable structure 539 includes second comb drives534 and first and second connector beams 553 and has a thickness rangingfrom 15 to 200 microns and preferably approximately 85 microns.

Means including spaced-apart first and second outer springs 536 and 537and optional central spring 538 are included within rotary electrostaticmicroactuator 507 for movably supporting second comb drives 534 and theremainder of movable structure 539 over substrate 526. First and secondouter springs 536 and 537 are symmetrically disposed about radialcenterline 543 and central spring 538 extends between first and secondsets 531 and 532 of comb drive assemblies. Each of the springs 536-538,when in its rest position as shown in FIG. 1, is centered on a radialline extending through the virtual pivot point of microactuator 507.Central spring 538 extends along radial centerline 543. The springs arespaced approximately 20 to 30 degrees apart about the virtual pivotpoint of microactuator 507.

Each of the springs 536-538 is formed from a single beam-like springmember 556 having a first or inner radial end portion 556 a and a secondor outer radial end portion 556 b. The inner radial end portion 556 a ofthe spring member 556 is secured or coupled to substrate 526 at ananchor 557. The balance of the spring member 556 is spaced above thesubstrate by an air gap. The outer radial end portion 556 b of outersprings 536 and 537 is secured or coupled to the outer radial extremityof the adjacent second comb drive bar 551 and the outer radial endportion 556 b of central spring 538 is secured or coupled to the outerradial extremity of the adjacent second comb drive bars 551 forming theinner boundary of each of first and second sets 531 and 532 of combdrive assemblies. Each of the spring members 556 has a length rangingfrom 300 to 3000 microns and preferably approximately 1000 microns andhas a width ranging from one to 20 microns and preferably approximatelyfive microns. First and second elongate sacrificial bars 558 and 559 ofthe type described in U.S. Pat. No. 5,998,906 extend along oppositesides of each spring member 556 for ensuring even etching and thus thedesired rectangular cross section of the spring member 556. Springs536-538 each have a thickness similar to movable structure 539 andpreferably the same as movable structure 539. Although three springs536-538 are disclosed for microactuator 507, it should be appreciatedthat two such springs or greater than three such springs can beprovided. In addition, although first and second comb drive assemblies527 and 528 are shown and described as being disposed between outersprings 536 and 537, some or all of such comb drive assemblies 527 and528 can be disposed outside of the springs 536 and 537.

Each of the second comb drives 534 of first and second comb driveassemblies 527 and 528 is movable in a first direction of travel aboutthe pivot point of microactuator 507 between a first or intermediateposition in which comb fingers 547 and 552 of the comb drive assemblyare not substantially fully interdigitated and a second position inwhich such comb fingers 547 and 552 are substantially fullyinterdigitated. Each of the comb drive assemblies 527 and 528 is shownin FIG. 1 in the first position in which the comb fingers 547 and 552 ofeach comb drive assembly 527 and 528 are not substantially fullyinterdigitated. More specifically, comb fingers 547 and 552 of thesecond comb drive assembly 528 in first set 531 and of the first combdrive assembly 527 in second set 532 are partially interdigitated whilein the first position and comb fingers 547 and 552 of the first combdrive assembly 527 in first set 531 and of the second comb driveassembly 528 in second set 532 are not interdigitated while in the firstposition. It can thus be seen that although comb fingers 547 and 552 canbe partially interdigitated when a second comb drive 534 is in its firstposition, the comb fingers can alternatively be disengaged and thus notinterdigitated when the second comb drive is in its first position. Whenin their second position, movable comb fingers 552 extend betweenrespective stationary comb fingers 547. The movable comb fingers 552approach but preferably do not engage stationary bar 546 of therespective first comb drive 533 and, similarly, the stationary combfingers 547 approach but preferably do not engage movable bar 551 of therespective second comb drive 534.

Each of the second comb drives 534 of first and second comb driveassemblies 527 and 528 is also movable in a second direction of travelabout the pivot point of microactuator 507 from the intermediateposition shown in FIG. 1 to a third position in which the comb fingers547 and 552 are spaced apart and fully disengaged (not shown). When combfingers 547 and 552 of one comb drive assembly 527 or 528 in a set 531or 532 are in the first position, the comb fingers of the other combdrive assembly 527 or 528 are in the third position. Thus each secondcomb drive 534 is movable between the second position, in which combfingers 547 and 552 are substantially fully interdigitated, to the firstor intermediate position, in which the comb fingers are notsubstantially fully interdigitated, to the third position, in which thecomb fingers are fully disengaged and spaced apart.

Electrical means is included for driving the second comb drives 534between their first and second positions. Such electrical means includesa suitable controller and preferably a controller and voltage generator561 that is electrically connected to the first and second comb drives533 and 534 of microactuator 507. In this regard, the outer radial endportion 546 b of each first comb drive bar 546 is electrically connectedby means of a lead 562 to a bond pad 563 provided on a side ofmicroactuator 507. Movable structure 539 is electrically connected by alead 566 to a bond pad 567 also provided on a side of substrate 526. Thelead 566 extends from such bond pad 567 to inner radial portion 556 a ofsecond spring 536. The bond pads 563 and 567 are electrically coupled bysuitable wires or leads 568 to controller and power supply 561.

Means in the form of a closed loop servo control can optionally beincluded in controller 561 or related control electronics for monitoringthe position of movable structure 539 relative to substrate 526. Forexample, controller 561 can include a conventional algorithm formeasuring the capacitance between comb fingers 552 of movable combdrives 534 and comb fingers 547 of the stationary comb drives 533. Asignal separate from the drive signal to the comb drive members can betransmitted by the controller to the microactuator for measuring suchcapacitance. Such a method does not require physical contact between thecomb drive fingers. The position of optical element 506 can becalibrated to the capacitance of the microactuator 507 and thus theposition of the optical element can be monitored and controlled. Thismethod of servo control can be implemented at low cost and does notrequire extra optical components.

The structural components of microactuator 507, that is movablestructure 539, springs 536-538 and first comb drives 533, have the shapeof a truncated fan when viewed in plan (see FIG. 1). In this regard,such components resemble a truncated or foreshortened sector of acircle, that is such components do not extend to the virtual pivot pointof microactuator 507 but instead are spaced radially outwardly from suchvirtual pivot point. As such, the virtual pivot point of microactuator507 intersects the plane of substrate 526 at a point outside theconfines of the components of such actuator and more specificallyoutside the confines of movable structure 536. Springs 536 and 537 andmovable structure 539 subtend an angle about the virtual pivot point ofmicroactuator 507 of less than 180° and preferably less than 90°. In thespecific embodiment of microactuator 507 shown in FIG. 1 and discussedabove, springs 536 and 537 and movable structure 539 subtend an angle ofapproximately 45 degrees about such virtual pivot point.

In operation and use, movable structure 539 is movable about the virtualpivot point of microactuator 507 in opposite first and second angulardirections from its at rest or intermediate position shown in FIG. 1.When movable structure 539, and thus reflector 506, moves in acounterclockwise direction about such virtual pivot point, second combdrives 534 of the second comb drive assembly 528 in each of the firstand second sets 531 and 532 move to their respective second positions sothat comb fingers 547 and 552 of the second comb drive assemblies 528are substantially fully interdigitated. When movable structure 531 ismoved in a clockwise direction about the virtual pivot point ofmicroactuator 507, second comb drives 534 of the first comb driveassembly 527 in each of the first and second sets 531 and 532 move totheir respective second positions so that comb fingers 547 and 552 ofthe first comb drive assemblies 527 are substantially fullyinterdigitated. Springs 536-538 provide radial rigidity to movablestructure 539 for inhibiting snap over of the interdigitated combfingers 547 and 552. Springs 536-538 provide radial rigidity to movablestructure 539 for inhibiting snap over of comb fingers 547 and 552.

When it is desired to rotate movable structure 539 and thus reflector506 in a clockwise direction about the virtual pivot point ofmicroactuator 507, in one preferred method a voltage potential issupplied by controller 561 to stationary comb drives 533 of first driveassemblies 527 so as to cause comb fingers 552 of the respective movablecomb drives 534 to be electrostatically attracted to comb fingers 547 ofthe stationary comb drives 533. Such attraction force causes combfingers 552 to move towards and interdigitate with comb fingers 547. Theamount of such interdigitation, and thus the amount movable structure539 and reflector 506 pivot about the virtual pivot of microactuator507, can be controlled by the amount of voltage supplied to thestationary comb drives 533 of the first comb drive assemblies 527. Whenit is desired to pivot movable structure 539 and reflector 506 in acounterclockwise direction about the virtual pivot axis of microactuator507, a suitable voltage potential can be supplied to stationary combdrives 533 of second comb drive assemblies 528 so as to cause combfingers 552 of the respective movable comb drives 534 to move towardsand interdigitate with comb fingers 547 of the second comb driveassemblies 528. As can be seen, the second comb drives 534 of one offirst comb drive assemblies 527 or second comb drive assemblies 528 arein their second positions when the second comb drives 534 of the otherof second comb drive assemblies 528 or first comb drive assemblies 527are in their first positions.

Suitable voltage potentials to drive comb drive assemblies 527 and 528can range from 20 to 200 volts and preferably range from 60 to 150volts. Microactuator 507 is capable of a +/−1.5 degrees of pivotablerotation about the virtual pivot point of the microactuator 507, that isrotational movement of 1.5 degrees in both the clockwise and thecounterclockwise directions for an aggregate pivotal movement of threedegrees when drive voltages of 120 or 140 volts are utilized. The amountof a angular deflection of movable structure 539 about such virtualpivot point is dependent on the number of comb fingers 547 and 552, theelectrostatic gap between the comb fingers and the length and width ofsprings 536-538.

Radially-extending springs 536-538 provide radial rigidity and stiffnessto movable second comb drives 534 and thus inhibit snap over of the combfingers 547 and 552 during interdigitation. The nonfolded design ofsprings 536-538 enhances out-of-plane stiffness, that is stiffness inmicroactuator 507 that is out of the plane of movable structure 539.Such out-of-plane stiffness facilitates support of the relatively largereflector 506 and inhibits misalignments between the reflector 506 anddiffraction grating 504 during operation of microactuator 507.

Microdevices incorporating microactuators, like microactuator 507, canbe provided that are balanced so that the movable portions of suchactuators, and elements or objects moved thereby, are not undesirablymoved when external accelerations or forces are applied to the device.An embodiment of such microdevice is shown in FIGS. 2-8. Balancedapparatus or microdevice 652 shown therein includes at least onemicroactuator coupled to a movable member or element, such asmicroreflector 506, for moving such element and more specifically forpivoting the microreflector 506. The microdevice is balanced to inhibitundesirable movement of the reflector 506 from externally appliedaccelerations to the device and can be used in any suitable applicationsuch as in a tunable laser. In one preferred embodiment, the balancedmicrodevice 652 includes a first microactuator or motor 653 which ispreferably a MEMS-based microactuator of any suitable type and morepreferably an electrostatic microactuator similar to microactuator 507described above. Like reference numerals have been used to describe likecomponents of microactuators 507 and 653.

Microactuator 653 has at least one and preferably a plurality of firstand second comb drive assemblies 656 and 657 carried by substantiallyplanar substrate 526 and arranged on the substrate in first and secondsets 658 and 659 (see FIGS. 2 and 6). Each of the first and second combdrive assemblies includes a first comb drive member or comb drive 662mounted on substrate 526 and a second comb drive member or comb drive663 overlying the substrate. At least first and second spaced-suspensionbeams or spring members 664 and 666 are included in microactuator 653for supporting or suspending second comb drives 663 over the substrate526 and for providing radial stiffness to the movable second comb drives663. The second comb drives 663 are part of a movable portion orstructure 667 overlying the substrate 526.

First and second comb drive assemblies 662 and 663, first and secondsprings 664 and 666 and the remainder of movable structure 667 areformed atop substrate 526 by a second or top layer 668 made from a waferof any suitable material such as silicon. Top layer or wafer 668 has athickness ranging from 10 to 200 microns and preferably approximately 85microns and is preferably fusion bonded to the substrate 526 by means ofa silicon dioxide layer 669 (see FIG. 4). The components ofmicroactuator 653 are preferably etched from top wafer 668 by anysuitable technique and preferably by the techniques discussed above withrespect to microactuator 507. Springs 664 and 666 and movable structure667 are spaced above the substrate 526 by an air gap 671 that rangesfrom 3 to 30 microns and preferably approximately 15 microns, so as tobe electrically isolated from the substrate 526.

First and second sets 658 and 659 of comb drive assemblies aresymmetrically disposed about a radial centerline 672 of microactuator653 and each include a first comb drive assembly 656 and a second combdrive assembly 657 (see FIG. 2). First comb drive assembly 656 of thefirst set 658 and second comb drive assembly 657 of the second set 659are disposed adjacent centerline 672. A second comb drive assembly 657is spaced away from the centerline 672 in the first set 658 and a firstcomb drive assembly 656 is spaced away from the centerline in the secondset 659 so as to be adjacent the respective sides of microactuator 653.Each of the first and second comb drive assemblies 656 and 657 has alength ranging from 300 to 3000 microns and preferably approximately1300 microns, and commences a radial distance ranging from 500 to 5000microns and preferably approximately 2000 microns from the pivot pointof microactuator 653.

First comb drive 662 of each of first and second comb drive assemblies656 and 657 is immovably secured to substrate 526. Each first comb drive662 has a radially-extending truss or bar 676 provided with a first orinner radial portion 676 a and second or outer radial portion 676 b (seeFIGS. 5 and 8). A plurality of first comb drive fingers or comb fingers677 extend from one side of bar 676 in radially spaced-apart positionsalong the length of the bar. Comb fingers 677 can be of any suitableshape and are preferably approximately arcuate in shape. In a preferredembodiment, piecewise linear segments are used to form comb fingers 677for approximating such an arcuate shape.

Second comb drives 663 are spaced above substrate 526 so as to bemovable relative to the substrate and first comb drives 662. The secondcomb drives 663 have a construction similar to first comb drives 662and, more specifically, are formed with a radially-extending truss orbar 681 having a first or inner radial portion 681 a and a second orouter radial portion 681 b (see FIGS. 5 and 8). A plurality of secondcomb drive fingers or comb fingers 682 extend from one side of bar 681in radially spaced-apart positions along the length of the bar 681. Combfingers 682 are substantially similar in construction in size to combfingers 677 of the related comb drive assembly 656 or 657. In each ofcomb drive assembly sets 658 and 659, the second comb drives 663 of thefirst and second comb drive assemblies 656 and 657 share a second bar681 such that the two second comb drives 663 are back-to-back. Movablecomb fingers 682 of each second comb drive 663 are offset relative tothe respective stationary comb fingers 677 so that the movable combfingers 682 can interdigitate with the stationary comb fingers 677 whenthe second comb drive 663 is pivoted about the virtual pivot point orpivot point of microactuator 653 towards the respective first comb drive662.

Each of first and second comb fingers 677 and 682 are optionallyinclined relative to respective bars 676 and 681, that is each combfinger is joined to the respective bar at an oblique angle as opposed toa right angle (see FIG. 3). The inclination angle 683 at which each combfinger 677 and 682 is joined to its respective bar 676 or 681, measuredfrom a line extending normal to the bar, can range from zero to fivedegrees and is preferably approximately three degrees. Stationary combfingers 677 are inclined at such inclination angle 683 towards outerradial portion 376 b of the stationary bar 676. Conversely, movable combfinger 682 are inclined at inclination angle 683 towards inner radialportion 681 of the movable bar 681. The inclination angle 683 of firstcomb fingers 677 is preferably equal to the inclination angle of secondcomb fingers 682. In one preferred embodiment, the equation defining theshape of each first and second comb finger 677 and 682 is:R ₂(θ)=R ₀ +mθ+b,where R₀ is the nominal radius of the comb finger measured from thevirtual pivot point of microactuator 653, m is the slope and b is theoffset of the comb finger from the nominal radius.

Each second comb drive finger 682 is optionally offset relative to themidpoint between the adjacent pair of first comb drive fingers 677between which the second comb drive finger interdigitates when secondcomb drive 663 is electrostatically attracted to first comb drive 662.Each adjacent pair of first comb drive fingers 677 has a space 686therebetween, as shown most clearly in FIGS. 3 and 7. The midpointbetween an adjacent pair of first comb drive fingers 677 is representedby an imaginary midpoint line 687 in the figures. The initial offset ofeach first comb drive finger 677 from the respective midpoint line 687,measured when second comb drive 663 is in its rest position shown inFIGS. 2 and 17, can range from zero to two microns and is preferablyapproximately 0.75 microns in the illustrated embodiment. The offset ofcomb drive fingers 677 from midpoint line 687 has been exaggerated inFIG. 3 to facilitate the visualization and understanding thereof. Itshould be appreciated that comb fingers 677 and 682 which extend fromtheir respective comb drive bars in arcs having a constant radiusmeasured from the pivot point of microactuator 653 can be provided.

Although first and second comb fingers 677 and 682 can be identical inshape and size, the comb drive fingers of first microactuator 653 varyin size and shape. More specifically, second comb fingers 682 in firstcomb assembly 656 of the first set 658 of comb drive assemblies decreasein length in a linear manner from the inner radial extremity of secondor movable comb drive 663 to the outer radial extremity thereof.Similarly, second comb fingers 682 in second comb drive assembly 657 ofthe second set 659 of comb drive assemblies decrease linearly in lengthfrom the inner radial portion 681 a of second or movable comb bar 681 tothe outer radial portion 681 b of the second bar.

First and second comb fingers 677 and 682 can be of constant width, asthey extend outwardly from the respective bars 676 or 681, as with thecomb fingers 677 and 682 in first comb drive assembly 656 of first set658 and the comb fingers in second comb drive assembly 657 of second set659, or can vary in width along the length thereof. For example, each ofthe comb fingers 677 and 682 in second comb drive assembly 657 of thefirst set 658 and in first comb drive assembly 656 of the second set 659has an inner of proximal portion that is wider than the outer or distalportion of such comb finger. Specifically, each first comb finger 677 insuch comb drive assemblies has an inner or proximal portion 691 and anouter or distal portion 692, as shown in FIGS. 5 and 8. Similarly, eachsecond comb finger 682 in such comb drive assemblies has an inner orproximal portion 693 and an outer or distal portion 694. Each innerportion 691 or 693 has a width ranging from 4 to 20 microns andpreferably approximately 10 microns, and each outer portion 692 and 694has a smaller width ranging from 2 to 12 microns and preferablyapproximately five microns. Each of the stationary inner portions 691has a length ranging from 40 to 150 microns and preferably approximately80 microns and preferably, as shown in FIG. 5, and decreases linearly inrelative length, that is after taking into consideration the increase inlength with radius of each comb drive finger to reflect the truncatedsector-shaped or pie-shaped configuration of the comb drive assemblies,from inner radial portion 676 a of the first bar 676 to outer radialportions 676 b of the first bar. Each of the movable inner portions 693has a length of ranging from 40 to 150 microns and preferablyapproximately 80 microns and increases linearly in relative length frominner radial portion 681 a to outer radial portions 681 b of the secondbar 681.

The outer radial portions 681 b of the second bars 681 are joined to aconnector bar or shuttle 696 extending substantially perpendicularly tothe bars 681 and arcuately relatively to the virtual pivot point ofmicroactuator 653. Shuttle 696 is a substantially rigid member and isincluded in movable structure 667 of the microactuator 653. The shuttle696 forms the outer radial periphery of microactuator 653 and extendssideways to each of the sides of the microactuator.

Means including at least first and second springs 664 and 666 areprovided in rotary electrostatic microactuator 653 for movablysupporting second comb drives 663 and the remainder of movable structure667 over the substrate 526. First and second springs 664 and 666 aresymmetrically disposed about radial centerline 672 and, when in theirrespective rest positions shown in FIG. 2, are each centered on a radialline extending through the virtual pivot point of first microactuator653. The springs 664 and 666 are angularly spaced apart approximately 20to 30 degrees about the virtual pivot point of microactuator 653. Firstand second comb drive assemblies 656 and 657 are disposed betweensprings 664 and 666, although at least some of the comb drivesassemblies can optionally be disposed outside of the springs.

Each of springs 664 and 666 can be of any suitable type and ispreferably formed from a single beam-like spring member 698 having afirst or inner radial end portion 698 a and a second or outer radial endportion 698 b (see FIGS. 2 and 6). It should be appreciated however thatfirst and second springs 664 and 666 can have other configurations whenin their rest positions, such as being pre-bent as disclosed in U.S.Pat. No. 5,998,906, and be within the scope of the present invention.The inner radial end portion 698 a is coupled or secured to substrate526 at an anchor 699 so as to suspend the spring member 698 above thesubstrate a distance equal to air gap 671. The outer radial end portion698 b of each spring member 698 is secured to shuttle 696 and thuscoupled to the second comb drive 663 of first microactuator 653. Each ofthe spring members 698 has a length ranging from 300 to 3000 microns andpreferably approximately 1000 microns and has a width ranging from 1 to20 microns and preferably approximately four microns. First and secondelongate sacrificial bars 701 of the type described in U.S. Pat. No.5,998,906 extend along each side of each spring member 698 for ensuringeven etching of the desired rectangular cross section of the springmember 698. Each of springs 664 and 666 has a thickness similar to thethickness of movable structure 667, and preferably the same as movablestructure 667. In the embodiment illustrated in FIGS. 2-8, the springs664 and 666 form the respective first and second radial sides of firstmicroactuator 653.

Each of second comb drives 663 is movable in opposite first and secondangular directions about the virtual pivot point of microactuator 653 inthe same manner as discussed above with respect to microactuator 507. Ingeneral, each second comb drive 663 is movable in the first angulardirection about the pivot point between a first or intermediate positionin which comb fingers 677 and 682 of respective comb drive assembly arenot substantially fully interdigitated and a second position in whichsuch comb fingers are substantially fully interdigitated. Each of firstand second comb drive assemblies 656 and 657 is shown in FIG. 2 in theirfirst positions and second comb drive assemblies 657 are shown in FIG. 6in their second positions. Each of the second comb drives 663 is alsomovable in the second angular direction about the pivot point ofmicroactuator 653 between its intermediate position and a third positionwhich comb fingers 677 and 682 are spaced apart and fully disengaged.First comb drive assemblies 656 are shown in FIG. 6 in their spacedapart and fully disengaged third positions.

Means is included within first microactuator 653 for limiting theangular movement of movable structure 667 between its extreme angularpositions about the virtual pivot point of the microactuator. In thisregard, a bumper 706 is formed on shuttle 696 for alternatively engagingfirst and second stops 707 formed on substrate 526 from top wafer 668.

Electrical means is included in controller 561 or related controlelectronics for driving second comb drives 663 between their first andsecond positions. Such electrical means include a suitable controller,such as controller and voltage generator 561 discussed above withrespect to microactuator 507, that is electrically connected to thefirst and second comb drives 662 and 663 of microactuator 653. In thisregard, the inner radial end portion 676 a of each first comb drive 662is electrically connected to controller 561 by means of a lead 708extending to a bond pad 709 provided along one side of substrate 526.Movable structure 667 is electrically connected to controller 561 by alead 711 extending to a bond pad 712 also provided on a side ofsubstrate 526. Bond pads 709 and 712 are electrically coupled bysuitable wires or other leads (not shown) to controller 561. Means inthe form of a closed loop servo control system can optionally beincluded in controller 561 or related control electronics for monitoringthe position of movable structure 667 relative to substrate 526. Forexample, controller 561 can include a conventual algorithm of the typediscussed above the respect to microactuator 507 for measuring thecapacitance between comb fingers 682 of movable comb drives 663 and combfingers 677 of stationary comb drives of 662.

The structural components of first microactuator 653, that is movablestructure 667, first and second springs 664 and 666 and first combdrives 662, have the shape of a truncated fan when viewed in plan (seeFIGS. 2 and 6). In this regard, such components resemble a truncated orforeshortened sector of a circle. Such components do not extend to thevirtual pivot point of microactuator 653, but instead are spacedradially outwardly from such virtual pivot point. As such, the virtualpoint of the microactuator 653 intersects the plane of substrate 526 ata point outside the confines of the components of microactuator 653 and,more specifically, outside the confines of movable structure 667.Springs 664 and 666 and movable structure 667 subtend an angle about thevirtual pivot point of microactuator 653 of less than 180 degrees andpreferably less than 90 degrees. More preferably, springs 664 and 666and movable structure 667 subtend an angle of approximately 45 degreesabout such virtual pivot point.

Movable structure 667 is rotatable about the virtual pivot point ofmicroactuator 653 in opposite first and second angular directions fromits at-rest or intermediate position shown in FIG. 2 in the same manneras discussed above with respect to microactuator 507. In general, whenmovable structure 667 moves in a clockwise direction about such virtualpivot point, second comb drives 663 in first comb drive assemblies 656of each set 658 and 659 move to their respective second positions. Whenmovable structure is moved in an opposite counterclockwise directionabout such virtual pivot point, second comb drives 663 in second combdrive assemblies 657 of each set 658 and 659 move to their respectivesecond positions, as shown in FIG. 6.

Reflector 506 is coupled to microactuator 653. Specifically, thereflector 506 is carried by movable structure 667 in the same manner asdiscussed above with respect to microactuator 507 and extendsperpendicularly from the plane of microactuator 653. First and secondspaced-apart pads 713 and 714 are included on movable structure 667 forreceiving the reflector 506. First pad 713 extends from inner radial endportions 681 a of the second comb drives 663 of first set 658. Secondpad 714 extends from the end of shuttle 696 secured to first spring 664.Pads 713 and 714 are included in the coupling means or coupler ofmicrodevice 652 for connecting the reflector 506 to the microactuator653.

A counterbalance 726 is carried by substrate 526 and coupled to secondcomb drives 663 of first microactuator 653. The counterbalance orcounterbalancing means 726 optionally includes a second microactuatorand preferably a MEMS-based microactuator of any suitable type. Thecounterbalance more preferably includes a rotary electrostaticmicroactuator or any other suitable electrostatic microactuator. In onepreferred embodiment, shown in FIGS. 2 and 6, a balancing microactuator727 substantially similar to first microactuator 653 is included incounterbalance 726. Like reference numerals have been used in thedrawings to describe like components of microactuators 653 and 727.Stationary comb drive fingers or comb fingers 731 and movable comb drivefingers or comb fingers 732 of microactuator 727, identified in FIG. 6,are substantially similar to the comb fingers 676 and 682 in second combdrive assembly 657 of first set 658 and the comb fingers 676 and 682 infirst comb drive assembly 656 of second set 659 of microactuator 653.Each of the stationary comb fingers 731 has an inner portion 691 and anouter portion 692, and each of the movable comb fingers 732 has an innerportion 693 and an outer portion 694.

In the same manner as discussed above with respect to firstmicroactuator 653, movable structure 667 of balancing microactuator 727moves or rotates in first and second opposite angular directions about avirtual pivot point, identified as pivot point 723 in FIG. 2. Pivotpoint 723 is generally located at the intersection of straight linesdrawn from first and second springs 664 and 666, when in theirrespective rest positions, and radial centerline 672 of themicroactuator 727.

Electrical means is included for driving second comb drives 534 ofbalancing microactuator 727 between their first and second positions andcan include controller and voltage generator 561 used for controllingfirst microactuator 653. Controller 561 is electrically coupled tobalancing microactuator 727 in the same manner as discussed above withrespect to first microactuator 653 by means of bond pads 709 and 712 ofthe balancing microactuator 727. A suitable closed loop servo controlsystem, such as one using a conventional algorithm of the type discussedabove, can optionally be included in controller 561 or related controlelectronics for measuring the capacitance between comb fingers 677 and682 of balancing microactuator 727 to monitor the position of themovable structure 667 of the balancing microactuator 727.

Counterbalance 726 further includes a link 736 for coupling balancingmicroactuator 727 to first microactuator 653 and, more specifically, forcoupling second comb drives 663 of the balancing microactuator 727 tosecond comb drives 663 of the first microactuator 653. Link or leversassembly 736 is anchored to substrate 526 by a mount 737 formed from topwafer 668 and secured to the substrate 526 by silicon dioxide layer 669.Link 736 includes a lever arm 738 having first and second end portions738 a and 738 b and a central portion 738 c (see FIG. 2). Lever arm 738is pivotably coupled to mount 737 by means of a pivot assembly 741,which is X-shaped in conformation when viewed in plan and is formed fromfirst and second pivot arms 742 joined at their center to form a pivotpoint 743 for the pivot assembly. The pivot assembly 741 is elongate inshape, with the first ends of the pivot arms 742 joined in spaced-apartpositions to mount 737 and the second ends of the pivot arms joined inspaced-apart positions to lever arm 738 at central portion 738 c. Eachof the pivot arms 742 has a width and thickness similar to the width andthickness of spring members 698. First and second sacrificial bars 744,similar to sacrificial bars 701 discussed above, extend along each sideof the pivot arms 742 for ensuring even etching of the desiredrectangular cross section of the pivot arms.

First and second ends 738 a and 738 b of the level arm 738 are joined tothe respective shuttles 696 of first microactuator 653 and balancingmicroactuator 727 by respective first and second coupling members orcoupling springs 746 and 747 (see FIGS. 2 and 6). Springs 746 and 747are similar to first and second springs 664 and 666 and are each formedfrom a spring member 748 substantially similar to spring member 698.Each of the spring members 748 has one end secured to the respective endof lever arm 738 and the other end secured to a bracket 751 joined tothe respective shuttle 696. First and second sacrificial bars 752,substantially similar to sacrificial bars 701 discussed above, extendalong each side of each spring member 748 for the reasons discussedabove. Lever arm 738, pivot assembly 741, first and second couplingsprings 746 and 747 and brackets 751 are each formed from top wafer 668and overlie substrate 526 by the distance of air gap 671.

Counterbalance 726 optionally further includes one or more weights 756carried by movable structure 667 of balancing microactuator 727 tooffset or counterbalance the weight of reflector 506 mounted on themovable structure 667 of first actuator 653. In one preferredembodiment, a platform 757 is formed between the back-to-back movablebars 681 in each of the first set 658 of comb drive assemblies and thesecond set of 659 of comb drive assemblies of balancing microactuator727. Each of the platforms 757 is formed from top wafer 668. Weights 756are secured to platform 575 by any suitable means such as an adhesive(not shown). Movable structures 667 of first microactuator 653 andbalancing microactuator 727, reflector 506, weights 756 and link 736 areincluded in the movable framework 758 of balanced microdevice 652.

In operation and use of microdevice 652, each of first microactuator 653and balancing microactuator 727 are preferably driven by controller 561in the same manner as discussed above with respect to microactuator 507.Movement of movable structure 667 of microactuator 653 and reflector 506is obtained by providing suitable voltage potentials from controller 561to first and second comb drive assemblies 656 and 657 of themicroactuators 653 and 727.

The offset and inclined comb drive fingers of second comb driveassemblies 656 and 657 contribute to the stability of firstmicroactuator 653. In this regard, the bending of first and secondsprings 664 and 666 during interdigitation of comb fingers 677 and 682causes the springs 664 and 666 to shorten slightly and thus results inmovable comb fingers 682 following a noncircular trajectory. The actualtrajectory of comb fingers 682 during movement from their first tosecond positions is approximated by the equationR ₁(θ)=(R _(p) −Aθ ²)sec(θ),where A is given byA=(18R _(p) ²+2L ²−3LR _(p))/30L,with L being the length of spring members 698 and R_(p) being thedistance from the virtual pivot of first microactuator 653 to outerradial end portions 698 b of the spring members 698.

The complimentary inclination of first and second comb drive fingers 677and 682 relative to respective comb drive bars 676 and 681 results inthe comb fingers having a shape that compensates for the trajectory ofthe second comb drives 663. As discussed above, first comb drive fingers677 are inclined radially outwardly of the respective comb drive bar 676and second comb drive fingers 862 are inclined radially inwardly at aequal angle relative to the respective comb drive bar 681. Suchcooperative inclination of the comb fingers contributes to each secondcomb drive finger 682 being more centered relative to the respective parof adjacent first comb drive fingers 677 during interdigitation of thefirst and second comb drive fingers 677 and 682. Since the comb drivefingers remain more centered, radial stability is enhanced duringinterdigitation.

The offset alignment of second comb drive fingers 682 relative to firstcomb drive fingers 677 ensures that the second comb drive fingers 682will be substantially centered on midpoint line 687, as shown in FIG. 7,when the first and second comb drive fingers are fully interdigitated.When this is so, the derivative of the net side force between the combfingers 677 and 682 is substantially minimized and the side stability isincreased. The combination of inclined comb fingers and initial offsetallows the radial stability of the comb fingers to be maximizedthroughout the full deflection range. It should be appreciated theinvention is broad enough to cover microactuators having comb driveassemblies with comb fingers that are offset but not inclined orinclined but not offset.

The electrostatic forces exerted between the comb fingers ofmicroactuator 653 remain relatively constant during rotation of movablestructure 667. In this regard, the varying of the lengths of combfingers 682 along comb drive bars 681 in the first and second comb driveassemblies 662 and 663 adjacent radial centerline 672 and the varying ofthe lengths of inner portions 691 and 693 along the respective combdrive bars 676 and 681 in the first and second comb drive assembliesfarthest from centerline 672 minimizes undesirable spikes or peaks inthe electrostatic forces exerted between the respective first and secondcomb drives 662 and 663 during interdigitation of the respective combfingers 677 and 682.

In an exemplary illustration, FIG. 8 shows second comb drive 663 ofsecond comb drive assembly 657 of first set 658 in a partiallyinterdigitated position between its first position shown in FIG. 5 andits second position shown in FIG. 6. As can be seen therein, outerportion 692 of the stationary comb fingers 677 at outer radial portion676 b of first bar 676 is approximately half interdigitated between theinner portions 693 of adjacent movable comb fingers 682 at outer radialportion 681 b of the second bar 681. The amount of interdigitationbetween the outer portion 692 of stationary comb fingers 677 with theinner portion 693 of movable comb fingers 682 decreases in asubstantially linear manner from the outer radial portion to the innerradial portion of such first and second comb drive assemblies 6565 and657. The amount of interdigitation between outer portion 694 of themovable comb fingers 682 and the inner portion 691 of adjacentstationary comb fingers 677 at the inner radial portion of the secondcomb drive assembly 657 illustrated in FIGS. 5 and 8 is less than theamount of interdigitation between outer portion 692 of the stationarycomb fingers 677 and the inner portion 693 of adjacent movable combfingers 682 at the inner radial portion of such second comb driveassembly 657. The amount of interdigitation between outer portion 694and adjacent inner portions 691 decreases from the inner radial portionto the outer radial portion of such second comb drive assemblies 657.

Thus, as can be seen from FIG. 8, outer portions 692 sequentiallycommence interdigitation between adjacent inner portions 693, commencingat the outer radial portion of such second comb drive assembly 657 andcontinuing towards the inner radial portion of such second comb assembly657, during movement of the respective second comb drive 663 towards therespective first comb drive 662 and thereafter outer portions 694sequentially commence interdigitation between adjacent inner portions691, commencing at the inner radial portion and continuing to the outerradial portion of such second comb drive assembly 657, during furtherrotational movement of such second comb drive 663 about the virtualpivot point of first microactuator 653 towards the first comb drive 662of such second comb drive assembly 657. In this manner, any spike orpeak in the engagement force resulting from an outer portion 692 or 694interdigitating between the relatively wider inner portions 691 or 693is spread throughout the interdigitation of a complimentary pair offirst and second comb drives 662 and 663.

Counterbalance 726 serves to inhibit undesirable movements of the secondcomb drives 663 in first microactuator 653, and thus microreflector 506carried thereby, in the direction of travel of those components fromexternally applied accelerations to microdevice 652. As discussed above,first and second suspension members or springs 664 and 666 provideradial stiffness to first microactuator 653. As such, springs 664 and666 inhibit undesirable movements of the second comb drives 663 in theradial direction when forces or accelerations are externally applied tomicrodevice 652. The counterbalance 726 particularly minimizesundesirable movements in an angular direction about the pivot point offirst microactuator 653.

Angular movements of movable structure 667 of first microactuator 653about the virtual pivot point of the microactuator 653 arecounterbalanced by opposite angular movements of the movable structure667 of balancing microactuator 727 about the virtual pivot point 733,shown in FIG. 2, of the microactuator 727. Specifically, when secondcomb drive assemblies 657 of first microactuator 653 are driven bycontroller 561 from their first position to their second position, asshown in FIG. 6, second comb drive assemblies 657 of balancingmicroactuator 727 are moved from their first position to their thirdposition. Similarly, a clockwise movement of movable structure 667 offirst microactuator 653 is offset by a counterclockwise movement ofmovable structure 667 of balancing microactuator 727.

The mass of reflector 506 mounted on movable structure 667 may bebalanced by optional weights 756 mounted on movable structure 667 ofbalancing microactuator 727. The mass of optional weights 756 isadjusted so that the line between the virtual pivot of the firstmicroactuator 653 and the combined center of mass of movable structure667 of first microactuator 653 and reflector 506 is parallel to the linebetween the virtual pivot 733 of balancing microactuator 727 and thecombined center of mass of movable structure 667 of balancingmicroactuator 727 and optional weights 756. The mass of optional weights756 is also adjusted so that the product of the combined mass of movablestructure 667 of first microactuator 653 and reflector 506 with thedistance between the virtual pivot of first microactuator 653 and thecombined center of mass of movable structure 667 of first microactuator653 and reflector 506 is equal to the product of the combined mass ofmovable structure 667 of balancing microactuator 727 and optionalbalancing weights 756 with the distance between the virtual pivot 733 ofbalancing microactuator 727 and the combined center of mass of movablestructure 667 of balancing microactuator 727 and optional weights 756.Linear accelerations to device 652 then produce equal torques on bothfirst microactuator 653 and balancing microactuator 727 and equal forceson the two ends 738 a and 738 b of link 738 on pivot assembly 741.

If the perpendicular distances between the pivot point 743 and thecoupling springs 748 are not equal, but instead have a ratio R, then themass of optional weights 756 can be adjusted so that linearaccelerations to device 652 produce torques on first microactuator 653and balancing microactuator 727 that are not equal, but have the sameratio R. The force produced by linear accelerations acting on the massof lever arm 738 may also be included when balancing the forces on thetwo ends 738 a and 738 b of pivot assembly 741.

Other embodiments of the balanced microdevice of the present inventioncan be provided. Another balanced apparatus or microdevice 771 is shownin FIGS. 9 and 10 for moving any suitable object or element. In onepreferred embodiment, such an object is an optical element such as acollimating lens 503 carried by a lens substrate or block 515 havingfirst and second end portions 515 a and 515 b. In general, microdevice771 serves to move collimating lens 503 and is balanced to inhibitundesirable movement of the collimating lens 503 and lens block 515 fromexternally applied accelerations to the device. In one preferredembodiment, balanced microdevice 771 includes a microactuator or motor772 which is preferably a MEMS-based microactuator of any suitable typeand more preferably an electrostatic microactuator similar tomicroactuator 508 described above.

Linear microactuator 772 can be constructed in the manner discussedabove with respect to first microactuator 653 atop a planar substrate773 that is substantially similar to substrate 526 discussed above. Atleast one and preferably a plurality of first and second comb driveassemblies 776 and 777, which are preferably linear comb driveassemblies, are carried by substrate 773 and arranged on substrate 773in first and second sets 778 and 779. Each of the first and second combdrive assemblies 776 and 777 includes a first comb drive member or combdrive 781 mounted on substrate 773 and a second comb drive member orcomb drive 782 overlying the substrate 773. At least first and secondspaced-apart suspension members or spring members 783 and 784 areincluded in microactuator 772 for supporting or suspending the secondcomb drives 782 over the substrate 773 and for providing stiffness tothe second comb drives 794 in a direction along a longitudinalcenterline 786 of the microactuator 782.

The components of microactuator 772 are formed atop substrate 773 by atop layer or wafer substantially similar to top wafer 668 of firstmicroactuator 653. The top wafer is secured to substrate 773 in anysuitable manner and is preferably fusion bonded to the substrate bymeans of a silicon dioxide layer (not shown). The components ofmicroactuator 772 can be formed by any suitable means and are preferablyetched from the top layer by any of techniques discussed above withrespect to microactuator 508. Second comb drives 782 are part of amovable portion or structure 787 that, together with springs 783 and784, is spaced above substrate 773 by an air gap, similar to air gap 671discussed above with respect to first microactuator 653, so as to beelectrically isolated from substrate 773.

First and second comb drive assemblies sets 778 and 779 optionallyextend parallel to each other in symmetrical disposition relative tolongitudinal centerline 786 of microactuator 772. A single first combdrive assembly 776 and a single second comb drive assembly 777 areprovided in each set 778 and 779 of comb drive assemblies. First combdrive 871 of each of first and second comb drive assemblies 776 and 777is immovably secured to substrate 773 and has a longitudinally-extendingtruss or bar 791 having first and second portions 791 a and 791 b. Aplurality of comb drive fingers or comb fingers 792 extend from one sideof bar 791 in longitudinally spaced-apart positions along the length ofthe bar.

Second comb drives 782 are spaced above substrate 773 so as to bemovable relative to the substrate and first comb drives 781. The secondcomb drives 782 have a construction similar to first comb drives 781and, more specifically, are each formed with a longitudinally—extendingtruss or bar 796 having first and second end portions 796 a and 796 b.The second comb drives 782 of each set 778 and 779 are disposedback-to-back and, as such, share a bar 796. A plurality of comb drivefingers or comb fingers 797 extend from each side of each bar 796 toform the back-to-back second comb drives 782 of each set 778 and 779.The comb fingers 797 on each side of bar 796 are longitudinally spacedapart along the length the bar 796.

Comb fingers 792 and 797 are substantially similar in construction. Eachof the comb fingers are preferably of the type disclosed inInternational Publication No. WO 00/62410 having an International FilingDate of Apr. 12, 2000 and as such are inclined and offset. As more fullydisclosed International Publication No. WO 00/62410, each of the combfingers is slightly inclined from a line extending normal to therespective bar 791 or 796. In addition, when each of the comb driveassemblies 776 and 777 is in its rest position, movable comb fingers 797are offset relative to a midpoint line extending between the adjacentpair of stationary comb fingers 792 into which such comb fingers 797interdigitate. In addition to the foregoing, the comb fingers 792 and797 in first set 778 of comb drive assemblies are similar inconstruction to certain of the comb fingers discussed above with respectto first microactuator 653. More specifically, the comb fingers in firstset 778 are each formed with a first or inner portion 801 and a secondor outer portion 802. The inner portion 801 of each such comb finger hasa width greater than the width of the respective outer portion 802. Thecomb fingers 792 and 797 in second set 779 of comb drive assemblies eachhave a constant width along the length thereof.

First and second springs 783 and 784 are substantially similar inconstruction to springs 664 and 666 discussed above and each include asingle spring member 806 and first and second sacrificial bars 807extending parallel to the spring member along each of the opposite sidesof the spring member. Each spring member 806 has a first end portion 806a and an opposite second end portion 806 b. First end portion 806 a ofeach spring members is coupled or secured to substrate 783 at an anchor808 and second end portion 806 b of each spring member is coupled orsecured to second comb drives 782. In this regard, an elongate bar orshuttle 809 is secured to the free second end portion 806 b of eachspring member 806. Shuttle 809 extends substantially perpendicular tosprings 783 and 784 when the springs are in their rest positions shownin FIG. 9. The second end portion 796 b of each movable bar 796 of thesecond comb drives 782 is perpendicularly joined to the portion ofshuttle 809 extending between springs 783 and 784. The shuttle 809 ispart of the movable structure 787 of microactuator 772. It should beappreciated that some of the first and second comb drive assemblies 776and 777 of microactuator can be disposed outside of springs 783 and 784.

Second comb drives 782 of each of first and second comb drive assemblies776 and 777 are movable in a first direction from their first orintermediate positions shown in FIG. 9, in which comb fingers 792 and797 are not substantially fully interdigitated, to a second position, inwhich the comb fingers 792 and 797 are substantially fullyinterdigitated. The second comb drives 782 are also movable from theirfirst position in an opposite second direction to a third position, inwhich the comb fingers 792 and 797 are spaced apart and fullydisengaged. The comb fingers of first comb drive assemblies 796 areshown in FIG. 10 in the second position, in which the comb fingers aresubstantially fully interdigitated, while the comb fingers of secondcomb drives assemblies 777 are shown in FIG. 10 in the third position,in which the comb fingers are spaced apart and fully disengaged. Firstand second springs 783 and 784 permit the movement of second comb drives782 and provide longitudinal rigidity to shuttle 809 and a second combdrives so as to inhibit snap over between interdigitated comb fingers792 and 797.

The interdigitation of the comb drive fingers of first comb driveassembly 776 serves to move shuttle 809 and the remainder of movablestructure 787 in a sideways direction substantially perpendicular tolongitudinal centerline 786 to a first position relative to substrate773, as shown in FIG. 10. The interdigitation of the comb drive fingersof second comb drive assemblies 777 serves to move shuttle 809 and theremainder of movable structure 787 in an opposition second direction toa second position relative the substrate 773 (not shown). Bumpers 811are provided on the first end portions 796 a of movable comb drive bars796 and on shuttle 809 for engaging respective stops 812 formed onsubstrate 773 to limit the sideways movement of the second comb drives782 and shuttle 809 and thus define the first and second positions ofthe shuttle 809 and the remainder of movable structure 787.

Electrical means is included for driving second comb drives 782 and theremainder of movable structure 787 between their first and secondpositions. Such electrical means includes a controller, such ascontroller 561. An electrical lead or trace 813 extends from first endportion 791 a of each first comb drive 781 to a bond pad 814 forpermitting electrical control signals to be supplied to the first combdrives 781. An additional electrical lead or trace 816 extends from thefirst end portion 806 a of the spring member 806 of first spring 783 toa bond pad 817 for permitting electrical control signals to be suppliedto the movable second comb drives 782. Bond pads 814 and 817 areelectrically coupled by suitable wires or leads (not shown) to thecontroller 561. Means in the form of a closed loop servo control system,such as the conventional algorithm discussed above, can optionally beincluded in controller 561 or related control electronics for measuringthe capacitance between comb fingers 792 and 797 to monitor the positionof the second comb drives 782 of microactuator 772.

A counterbalance 821 is carried by substrate 773 and coupled to secondcomb drive 782 of microactuator 772. In this regard, elongate shuttle809 extends forwardly of microactuator 772 and is formed with a platform822. Counterbalance or counterbalancing means 821 includes a leverassembly or coupler 826 that is carried by substrate 773 and serves tocouple collimating lens 503 and lens block 515, or any other suitablemovable member or optical element, to shuttle 809.

Lever assembly 826 is formed from the top wafer disposed atop substrate773 and includes an anchor or mount 827 rigidly secured to the substrate773. A lever arm 828 is provided and has opposite first and second endsportions 828 a and 828 b and a central portion 828 c. Central portion828 c of the lever arm is secured to mount 827 by a pivot assembly 829that is substantially similar to pivot assembly 741 described above. Inthis regard, pivot assembly 829 has first and second pivot arms 831joined at their center to form a pivot point 832. First and secondsacrificial bars 833 extends along each side of the pivot arms. One endof each of the pivot arms is joined to mount 827 and the other end ofeach of the pivot arms is joined to central portion 828 c of lever arm828.

First end portion 828 a of the lever arm is coupled to shuttle platform822 by means of an additional pivot assembly 836 substantially identicalto pivot assembly 829. The pivot arms 831 of pivot assembly 836 form apivot point 837 where they intersect at the center of the X-shaped pivotassembly 836. A mounting platform 838 is formed at second end portion828 b of lever arm. First end portion 515 a of lens block 515 is securedto platform 838 by any suitable means such as an adhesive. The lensblock 515 is preferably aligned relative to lever assembly 826 such thatthe substrate 515 extends along the centerline of lever arm 828. Leverarm 828 and pivot assemblies 829 and 836 of lever assembly 826 arespaced above substrate 773 by an air gap so as to be movable relative tothe substrate. An optional weight 839 can be secured to shuttle platform828 by any suitable means such as a adhesive (not shown). Movablestructure 787, collimating lens 503, lens block 515, lever assembly 826and weight 839 are included in the movable framework 841 of balancedmicrodevice 771.

In operation and use, first and second comb drive assemblies 776 and 777of microactuator 772 are preferably driven by the controller 561 in thesame manner as discussed above with respect to microactuator 508 to movecollimating lens 503 or any other suitable object. As shown in FIGS. 9and 10, movement of first comb drive assemblies 776 of the microactuator772 to their second positions causes lever arm 828 to pivot in acounterclockwise direction and thus move collimating lens 503 upwardlyrelative to substrate 773. Conversely, movement of second comb driveassemblies 777 from their first position to their second positionresults in lever arm 828 moving in a clockwise direction and thuscollimating lens moving downwardly relative to substrate 773. Pivotassembly 826 permits the lever arm 828 to pivot about pivot point 832and pivot relative to mount 827. Pivot assembly 836 pivotably coupleslever arm 828 to shuttle 809 for accommodating such pivotal movement ofthe lever arm 828 about pivot point 832. Since the amount of angularrotation of collimating lens 503 is substantially small, its upward anddownward movement is substantially. It can thus be seen that movement ofthe second comb drives 782 of microactuator 772 in a first directioncauses collimating lens 503 to move in a second direction substantiallyopposite to the first direction.

In a manner similar to counterbalance 726, counterbalance 821 of secondbalance microdevice serves to inhibit undesirable movements of thesecond comb drives 782 of microactuator 772, and thus collimating lens503, in the direction of travel of those components from externallyapplied accelerations to microdevice 771. As discussed above, first andsecond springs 783 and 784 of microactuator 772 provide stiffness tosecond comb drives 782 along the longitudinal centerline 786 ofmicrodevice 771. Counterbalance 821 particularly inhibits undesirablemovements of the second comb drives 782, in a direction substantiallyperpendicular to centerline 786, between the first, second and thirdpositions of the comb drives. In this regard, the object or elementbeing moved by microactuator 772, in this instance collimating lens 503and lens block 515, serves as part of the counterbalance of microdevice771. Factors contributing to the counterbalancing of the microdevice of771 include the aggregate mass of movable structure 787 and weight 839relative to the aggregate mass of lens block 515 and collimating lens503, the location of the center of mass of movable structure 787 andweight 839 relative to the center mass of lens block 515 and collimatinglens 503 and the length of first end portion 828 a of lever arm 828relative to the length of second end portion 828 b of the lever arm 828.The mass of framework 841 and the distance from pivot 832 to theframework center of mass may also be considered.

Another embodiment of the balanced microdevice of the present inventionis shown in FIGS. 11 and 12. Microdevice 889 therein can be used formoving or rotating any suitable object or element such as collimatinglens 503. Balanced microdevice 889 has a rotary electrostaticmicroactuator and preferably a fan-shaped rotary electrostaticmicroactuator. A balanced microdevice 889 having a particularlypreferred rotary electrostatic microactuator 891 is shown in FIGS. 11and 12. Balanced rotary microactuator 891 is formed from a substrate 892substantially similar to substrate 526. A movable or rotatable member,in the exemplary embodiment shown as a platform 893, overlies substrate892. A plurality of first and second comb drive assemblies 896 and 897are carried by substrate 892 for rotating platform 893 in opposite firstand second angular directions about an axis of rotation extendingperpendicular to substrate 892 and shown as a pivot point 898 in FIGS.11 and 12. Each of the first and second comb drive assembles 896 and 897includes a first comb drive member or comb drive 901 mounted onsubstrate 892 and a second comb drive member or comb drive 902 overlyingthe substrate 892. First and second spaced-apart springs 903 and 904 areincluded in microactuator 891 for supporting or suspending second combdrives 902 and platform 893 over the substrate 892 and for providingradial stiffness to such comb drives and platform. Second comb drives902 and platform 893 are part of a movable portion or structure 906 ofmicroactuator 892.

Substrate 892 is substantially similar to substrate 526. Platform 893,first and second comb drive assemblies 896 and 897, first and secondsprings 903 and 904 and the other components of microactuator 891 areformed atop substrate 892 by a second or top layer or wafer 907substantially similar to top wafer 668 discussed above. The top layer orwafer 907 is preferably fusion bonded to substrate 892 by means of asilicon dioxide layer (not shown). The components of microactuator 891are formed from top wafer 907 by any suitable means and preferably byany of the techniques discussed above.

At least one and preferably a plurality of first comb drive assemblies896 are included in balanced rotary microactuator 891 and angularlydisposed about pivot point 898 for driving movable structure 906 in aclockwise direction about the pivot point 898.

At least one and preferably a plurality of second comb drive assemblies897 are included in microactuator 891 for driving movable structure 906in a counterclockwise direction about pivot point 898. The comb driveassemblies of microactuator 891 are arranged in a first or inner radialset 911 symmetrically disposed about radial centerline 912 ofmicroactuator 891 and in a second or outer radial set 913 symmetricallydisposed about radial centerline 912. Each of the comb drive assemblies896 and 897 extends substantially radially from pivot point 898 and, inthe aggregate, subtends an angle of approximately 180 degrees or less,preferably approximately 120 degrees or less and more preferablyapproximately 90 degrees. As such, microactuator 891 has a fan likeshape when viewed in plan, as shown in FIGS. 11 and 12. Themicroactuator 891 has a base 916 extending substantially perpendicularlyof radial centerline 912, and pivot point 898 is disposed adjacent based916. The microactuator 891 has an arcuate outer radial extremity 917resembling the arc of a circle centered on pivot point 898 and a radialdimension from pivot point 898 to outer radial extremity 917 rangingfrom 1000 to 2500 microns and preferably approximately 1600 microns.

Two first comb drive assemblies 869 and two second comb drive assembles897 are included in inner set 911 of comb drive assemblies. The firstcomb drive 901 in each comb drive assembly of inner set 911 has aradially-extending bar 918 having a first of inner end portion 918 a anda second or outer end portion 918 b. A plurality of comb drive fingersor comb fingers 918 extend from one side of the bar 918 in radiallyspaced-apart positions along the length of the bar. The second combdrive 902 in each comb drive assembly of inner set 911 is formed from aradially-extending bar 921 having a first or inner end portion 921 a anda second or outer end portion 921 b. A plurality of comb drive fingersor comb fingers 922 extend from one side of the bar towards therespective first comb drive 901 in radially spaced-apart positions alongthe length of the bar. Comb fingers 919 and 922 can be of any suitablesize and shape and are preferably arcuate in shape. In a preferredembodiment, piecewise linear segments are used to form the comb fingers919 and 922 for approximating such an arcuate shape.

Although the comb fingers 919 and 922 can have a constant width alongthe length thereof, each of the comb fingers preferably has a first orinner portion 923 and a second or outer portion 924. The inner portion923 has a width greater than the width of outer portion 924 for reasonsdiscussed above. As shown in FIG. 11, comb fingers 919 and 922 arepartially interdigitated when in their first rest position.Specifically, outer portions 924 of stationary comb fingers 919 areinterdigitated with outer portions 924 of movable comb fingers 922.

The inner end portion 921 a of the movable bar 921 spaced farthest fromradial centerline 912 on each side of inner set 911 of first and secondcomb drive assemblies is joined to platform 893. The outer end portion921 b of each of the movable bars 921 in inner set 911 is joined to arigid shuttle 926 which is substantially arcuate in shape. The arcuateshuttle 926 is part of the movable structure 906 of balanced rotarymicroactuator 891.

Although springs 903 and 904 can be of any suitable type, each of thesprings preferably consists of a single beam-like member 927 having afirst or inner end portion 927 a and a second or outer end portion 927b. The inner end portion 927 a of each of the spring members is coupledto substrate 892 and, more specifically, is secured to a mount 928 thatis formed from top wafer 907 and is rigidly joined to substrate 892. Theinner end portions 927 a are each joined to the mount 928 at pivot point898. Each of the spring members 927 extends between two adjacent movablebars 921 and the outer end portion 927 b of each spring member is joinedto an end of arcuate shuttle 926. First and second springs 903 and 904are angularly spaced apart a distance of approximately 70 degrees and,when viewed together in plan, are substantially V-shaped.

A plurality of first and second comb drive assemblies 896 and 897 areincluded in outer set 913 of comb drive assemblies. More specifically,two first comb drive assemblies 896 and two second comb drive assemblies897 are included in the outer set 913. The first comb drive 901 in eachcomb drive assembly 896 and 897 of outer set 913 is formed from aradially-extending bar 931 having a first or inner end portion 931 a anda second or outer end portion 931 b. A plurality of comb drive fingersor comb fingers 932 extend from one side of the stationary bar 931 inradially spaced-apart positions along the length of the bar. Each of thesecond comb drives 902 in outer set 913 is formed from a substantiallyradially-extending bar 933 having a first or inner end portion 933 a anda second or outer end portion 933 b. A plurality of comb drive fingersof comb fingers 934 extend from one side of the movable bar 933 towardsthe respective first comb drive 901 in radially spaced-apart positionsalong the length of the bar 933.

Although comb fingers 932 and 934 can be of any suitable size and shape,the comb fingers are preferably arcuate in shape and, like comb fingers919 and 922, are preferably formed from piecewise linear segments forapproximating such an arcuate shape. Comb fingers 932 and 934 are notsubstantially interdigitated when in their first or rest position, shownin FIG. 11. More specifically, the comb fingers 932 and 934 aredisengaged in the rest or intermediate position of FIG. 11. Comb fingers919, 922, 932 and 934 can optionally be inclined and offset in themanner discussed above with respect to the comb fingers of firstmicroactuator 653.

The inner end portion 933 a of each movable bar 933 is joined to arcuateshuttle 926 and is thus movable in unison with the movable bars 921 ofinner set 911 of comb drive assembles. The second comb drives 902 of thefirst comb drive assembly 896 and the second comb drive assembly 897symmetrically disposed relative to the radial centerline at the centerof outer set 913 face away from each other. The movable bar 933 of suchsecond comb drives 902 are interconnected by means of a platform 937that is preferably joined to the outer end portions 933 b of suchmovable bars.

Movable structure 906 is rotatable in first and second opposite angulardirections above pivot point 898. Movement of the second comb drives 902of first comb drive assemblies 896 from their first positions, shown inFIG. 11, to their second positions, in which the respective comb fingersthereof are substantially fully interdigitated, results in movablestructure 906 rotating in a clockwise direction about pivot point 898.Similarly, movement of the second comb drives 902 of second comb driveassemblies 897 from their first positions, shown in FIG. 11, to theirsecond positions, in which the comb fingers of such second comb driveassemblies are substantially fully interdigitated as shown in FIG. 12,results in movable structure 906 rotating in a counterclockwise positionabout pivot point 898. When the second comb drives 902 of one of firstand second comb drive assemblies 896 and 897 move to their secondpositions, the second comb drives 902 of the other of the comb driveassemblies 896 and 897 move to their third positions, in which the combfingers thereof are spaced apart and fully disengaged. First comb driveassemblies 896 are shown in their third positions in FIG. 12. Movablestructure 906 is capable of rotating plus and minus two to ten degreesand preferably approximately six degrees in each direction, for anaggregate rotation between its extreme angular positions ranging fromfour to 20 degrees and preferably approximately 12 degrees.

Means is included within balanced rotary microactuator 891 for limitingthe angular movement of movable structure 906 about pivot point 898. Inthis regard, a bumper 938 extends radially outwardly from outer platform937 and engages one of first and second stops 939 when movable structure906 is in either of its first and second extreme angular positions aboutpivot point 898.

The electrical means such as controller 561 can be utilized for drivingsecond comb drives 902 between their first and second positions. Firstcomb drives 901 of the first and second comb drive assemblies 896 and897 of inner set 911 spaced farthest from radial centerline 912 and allof the first comb drives 901 of outer set 913 are electrically connectedby means of leads 942 to at least one end and as shown first and secondbond pads 943. The first comb drives 901 of the first and second combdrive assemblies 896 and 897 of inner set 911 spaced closest to radialcenterline 912 are connected at respective inner end portions 918 a torespective first and second bond pads 944 disposed between first andsecond springs 903 and 904. Mount 928 additionally serves as a bond padfor electrically connecting second comb drives 902 and movable structure906 to controller 561. Means in the form of a closed loop servo controlsystem, for example a conventional algorithm of the type discussedabove, can optionally be included in controller 561 or related controlelectronics for measuring the capacitance between comb fingers 919 and922 and comb fingers 932 and 934 to monitor the position of movablestructure 906 relative to substrate 892.

Collimating lens 503 is coupled to movable structure 906 by means ofplatform 893. Specifically, first end portion 515 a of lens block 515 issecured to platform 893 by any suitable means such as an adhesive (notshown). The lens block 515 is centered on radial centerline 912 ofbalanced rotary microactuator 891 when movable structure 906 is in itsrest position shown in FIG. 11.

A counterbalance 946 is carried by substrate 892 and movable structure906 and thus, second comb drives 902. Counterbalance 946 includes aweight 947 secured to outer platform or coupler 937 by any suitablemeans such as an adhesive (not shown) and thus coupled to movablestructure 906 and second comb drives 902. The mass of weight 947 and itsposition on movable structure 906 are selected so that the center ofmass of movable structure 906, lens block 515, collimating lens 503 andweight 947, in the angular direction about pivot point 848, is locatedsubstantially at the pivot point 848. Movable structure 906, lens block515, collimating lens 503 and weight 947 are collectively referred to asthe movable framework 948 of balanced microdevice 889.

In operation and use, the rotary microactuator 891 of balancedmicrodevice 889 can be used in substantially the same manner asmicroactuator 772 to move collimating lens 503 or any other suitableobject. Rotation of movable structure 906 in its first and secondopposite angular directions about pivot point 848 results in collimatinglens 503 similarly rotating about pivot point 848. Since the amount ofangular rotation of collimating lens 503 is substantially small, theupward and downward movement of the collimating lens 503 issubstantially linear.

Counterbalance 946 serves to limit undesirable movements of thecollimating lens 503 about the axis of rotation of microactuator 891when external accelerations are applied to microdevice 889.

Another embodiment of the microdevice of the present invention is shownin FIGS. 13 and 14. Microdevice 950 shown herein, for moving anysuitable object or element 952, is preferably provided with a leverassembly and is preferably balanced. In one referred embodiment, such anelement 952 is an optical element such as a shutter plate or lightblocking member. For example, microdevice 950 can be used as a variableoptical attenuator or an on-off shutter in an optical communicationsystem. In this regard, microdevice 950 can be part of tunable laser ofthe type disclosed in U.S. patent application Ser. No. 09/728,212 filedNov. 29, 2000, the entire content of which is incorporated herein bythis reference.

In general, microdevice 950 includes a microactuator 954 that serves tomove the optical element 952 in a large displacement. A lever assembly956 including a pivot 958 and lever 960 is provided to couple togethermicroactuator 954 and optical element 952. The microdevice includes amovable portion 981 which causes lever 960 to pivot so as to moveoptical element 952 in a direction of travel. Element 952 issubstantially mechanically balanced to inhibit undesirable movement ofthe element in response to externally applied accelerations orvibrations.

In one preferred embodiment, microactuator or motor 954 is preferably aMEMS-based microactuator of any suitable type and more preferably alinear electrostatic microactuator similar to microactuator 772described above. Linear microactuator 954 can be constructed in themanner discussed above with respect to microactuator 772, atop a planarsubstrate 962, that is substantially similar to substrate 773 discussedabove. In general, linear microactuator 954 includes at least one andpreferably a plurality of first and second comb drive assemblies 972 and974, preferably linear comb drive assemblies, which are carried bysubstrate 962 and arranged on substrate 962 in first, second, third andfourth sets 964 through 968. Each of the first and second comb driveassemblies 972 and 974 includes a first comb drive member or comb drive976 mounted on substrate 962 and a second comb drive member or combdrive 978 overlying substrate 962. At least first and secondspaced-apart suspension members or spring members 977 and 979 areincluded in microactuator 954 for supporting or suspending the secondcomb drives 978 over substrate 962 and for providing stiffness to secondcomb drives 978 in a direction along a longitudinal centerline 965 ofmicroactuator 954.

The components of microactuator 954 are formed atop substrate 962 by atop layer or wafer substantially similar to top wafer 773 ofmicroactuator 772. The top wafer is secured to substrate 962 in anysuitable manner and is preferably fusion bonded to the substrate bymeans of a silicon dioxide layer (not shown). The components ofmicroactuator 954 can be formed by any suitable means and are preferablyetched from the top layer by any of techniques discussed above withrespect to microactuator 772. Second comb drives 978 are part of amovable portion or structure 981 that, together with springs 977 and979, is spaced above substrate 962 by an air gap, similar to air gap 671discussed above with respect to first microactuator 653, so as to beelectrically isolated from substrate 962.

First and second comb drive assemblies sets 964 and 966 extend parallelto each other in substantially symmetrical disposition relative tolongitudinal centerline 965 of microactuator 954. Similarly, third andfourth comb drive assemblies sets 968 and 970 extend parallel to eachother in substantially symmetrical disposition relative to longitudinalcenterline 965 of microactuator 954. A single first comb drive assembly972 and a single second comb drive assembly 974 are provided in eachcomb drive assemblies set 964 through 968. First comb drive 976 of eachof first and second comb drive assemblies 972 and 974 is immovablysecured to substrate 962 and has a longitudinally-extending truss or bar981 having first and second portions 982 a and 982 b. A plurality ofcomb drive fingers or comb fingers 984 extend from one side of bar 982in longitudinally spaced-apart positions along the length of the bar.

Second comb drives 978 are spaced above substrate 962 so as to bemovable relative to the substrate and first comb drives 976. The secondcomb drives 978 have a construction similar to first comb drives 976and, more specifically, are each formed with a longitudinally-extendingtruss or bar 980 having first and second end portions 980 a and 980 b.The second comb drives 978 of each set 964 through 970 are disposedback-to-back and, as such, share a bar 980. A plurality of comb drivefingers or comb fingers 986 extend from each side of each bar 980 toform the back-to-back second comb drives 978 of each set. The combfingers 986 on each side of bar 980 are longitudinally spaced apartalong the length the bar 980.

Comb fingers 984 and 986 are substantially similar in construction. Eachof the comb fingers 984 and 986 are preferably of the type disclosed inU.S. Pat. No. 6,384,510 and as such are inclined and offset. As morefully disclosed in U.S. Pat. No. 6,384,510, each of the comb fingers 984and 986 is slightly inclined from a line extending normal to therespective bar 980 and 982. In addition, when each of the comb driveassemblies 972 and 974 is in its rest position, movable comb fingers 986are offset relative to a midpoint line extending between the adjacentpair of stationary comb fingers 984 into which such comb fingers 986interdigitate.

First and second springs 977 and 979 are substantially similar inconstruction to springs 783 and 784 discussed above and each include asingle spring member 985 and first and second sacrificial bars 987extending parallel to the spring member along each of the opposite sidesof the spring member. Each of springs 977 and 979 has a first endportion 985 a and an opposite second end portion 985 b. First endportion 985 a of each spring members is coupled or secured to substrate962 and second end portion 985 b of each spring member is coupled tosecond comb drives 978. In this regard, an elongate bar or shuttle 990is secured to the free second end portion 985 b of each spring member.Shuttle 990 extends substantially perpendicular to springs 977 and 979when the springs are in their rest positions shown in FIG. 13. Thesecond end portion 980 b of each movable bar 980 of the second combdrives 978 is perpendicularly joined to shuttle 990.

Shuttle 990 is part of the movable structure 981 of microactuator 954.In particular, first and second comb drive assembly sets 964 and 966 aredisposed on one same side of shuttle 990 in substantially symmetricaldisposition with respect to the centerline 965 of microactuator 954.Third and fourth comb drive assembly sets 968 and 970 are disposed onthe opposite side of shuttle 990 in substantially symmetricaldisposition with respect to centerline 965 of microactuator 954.

Second comb drives 978 of each of first and second comb drive assemblies972 and 974 are movable in a first direction from their first orintermediate positions shown in FIG. 13, in which comb fingers 984 and986 are not substantially fully interdigitated, to a second position, inwhich the comb fingers are substantially fully interdigitated. Thesecond comb drives 978 are also movable from their first position in anopposite second direction to a third position (not shown), in which thecomb fingers 984 and 986 are spaced apart and fully disengaged.

First and second flexible springs 977 and 979 permits each of themovable comb drives 978 to move from a first or rest position shown inFIG. 13, in which comb fingers are not substantially fullyinterdigitated, to a second or actuated position shown in FIG. 14, inwhich comb fingers are substantially fully interdigitated. As usedherein, the term “not substantially fully interdigitated” is broadenough to cover comb fingers which are fully disengaged as well as combfingers which are partially interdigitated. Movement of second combdrives 978 to their respective second positions causes shuttle 990 tomove substantially in a linear direction of travel relative to substrate962.

Electrical means is included for driving second comb drives 978 and theremainder of movable structure 981 between their first and secondpositions. Such electrical means includes a controller, such ascontroller 561. An electrical lead or trace 996 extends from each firstcomb drive 972 to a bond pad 994 for permitting electrical controlsignals to be selectively supplied to appropriate first comb drives 972.An additional electrical lead or trace 997 extends from the first endportion 985 a of spring member 977 to a bond pad 995 for permittingelectrical control signals to be supplied to the movable second combdrives 978. Means in the form of a closed loop servo control system,such as the conventional algorithm discussed above, can optionally beincluded in controller or related control electronics for measuring thecapacitance between comb fingers 984 and 986 to monitor the position ofthe second comb drives 978 of microactuator 954.

Lever assembly 956 is coupled to microactuator 954 and includes a pivotassembly or pivot 958 and a lever arm or lever 960. Pivot or pivotassembly 958 is X-shaped in conformation when viewed in plan and isformed from first and second pivot arms 1000 and 1002 which are joinedat their center to form a pivot point 1004 of the pivot assembly 958.Each of pivot arms 1000 and 1002 has a first end portion 1000 a and 1002a joined to substrate 962 in spaced-apart positions and a second endportion 1000 b and 1002 b joined to lever arm 960 in spaced-apartpositions. Each of the pivot arms 1000 and 1002 is capable of bending orflexing and preferably has a cross-sectional configuration, both inshape and dimensions, similar to springs 977 and 979. Sacrificial bars1003, similar to sacrificial bars 987 discussed above, optionally extendalong the side of pivot arms for ensuring even etching of the desiredrectangular cross section of the pivot arms. Pivot assembly 958 permitslever 960 to pivot about pivot point 1004 in both clockwise andcounterclockwise directions from a first or rest position shown in FIG.13 to a second or actuated position shown in FIG. 14.

The elongate and substantially rigid lever 960 has a first extremity 960a coupled to microactuator 954 through flexural member 1006, an oppositesecond extremity 960 b coupled to an optical element 952, and a third orcentral portion 960 c coupled to pivot assembly 958. Third portion 960 cof lever 960 includes two extensions or couplers 1010 for coupling tosecond end portions 1000 b and 1002 b of each of first and second pivotarms 1000 and 1002 respectively. Lever 960 has a first length from thefirst extremity 960 a to pivot point 1004 and a second length from thesecond extremity 960 b to the pivot point 1004. The ratio of the secondlength to the first length can be adjusted to permit suitabledisplacement of optical element 952 in both clockwise andcounterclockwise directions. In one preferred embodiment, the firstlength is approximately 1100 microns and the second length isapproximately 2500 microns. Such dimensions provide a lever ratio ofabout 2.3, that is optical element 952 will translate 2.3 times of thetravel distance of shuttle 990. Microactuator 954 permit shuttle 990 totravel at least a distance of approximately 90 microns in both forwardand rearward directions, and thus moving element 952 in a direction oftravel through a distance at least 200 microns in both clockwise andcounterclockwise directions.

Flexible or bendable member 1006 is provided to couple first extremity960 a of lever 960 to microactuator 954. Specifically, the elongate andsubstantially linear coupler 1006 has first end portion 1006 a joined tofirst extremity 960 a of lever 960 and an opposite second end portion1006 b joined to movable structure 982 of microactuator 954. Coupler1006 preferably has a cross sectional configuration, including width andthickness, similar to the configuration of springs 977 and 979 so as topermit bending thereof during movement of lever 960. A rigid member 1008is provided to couple flexible member 1006 to microactuator 954.Specifically, rigid member 1008 is Z-shaped in conformation when viewedin plan and has first end portion 1008 a coupled to second end portion1006 b of flexural member 1006 and second end portion 1008 b coupled tobar 980 of second comb drive 978 of third comb drive assemblies set 968.

Movable components of microdevice 954 are substantially mechanicallybalanced to inhibit undesirable movement of element 952 in the directionof travel of element 952 in response to externally applied forces tomicrodevice 950. In this regard, mass of movable structure 981 ofmicroactuator 954, lever 960, and element 952 of microdevice 950 areadjusted so that the torque in the clockwise direction about pivot point1004 of pivot assembly 958 is substantially equal to the torque in thecounterclockwise direction about such pivot point. Any means can beutilized to adjust the dimensions and mass of the movable components ofmicrodevice 950 to achieve such mechanical balancing. For example, acounterbalance such as a weight or mass (not shown) can be attached tosuch movable components. Such a counterbalance is preferably carried bylever arm 960.

Element 952 can be any optical element such as a light blocking element,shutter, lens, and filter. In one preferred embodiment, element 952 is ashutter plate fabricated on substrate 962 during fabrication of othercomponents of microdevice 950. As shown in FIGS. 13 and 14, shutterplate 952 has a generally planar rectangular attenuation surface,however, the shape and the topography of the attenuation surface can bemodified to provide the desired level of attenuation and minimize powerconsumption. Shutter plate 952 as fabricated can be mounted to secondextremity 960 b of lever 960 by any suitable means. In one preferredembodiment, shutter plate 952 (shown as 952 b in FIGS. 13 and 14) iscoupled to lever 960 in a plane substantially perpendicular to the planeof substrate 962. As such, shutter plate 952 b can attenuate an opticalbeam 953 that lies in a plane parallel to the plane of substrate 962 andtravels in a path substantially perpendicular to the plane of theshutter disposition when in rest position, as shown in FIG. 14. Shutterplate 952 (shown as 952 a in phantom lines in FIG. 13) can also becoupled to lever 960 in a plane parallel to the plane of substrate 962shown in FIG. 13 so as to at least partially overlie an opening (notshown) defined by substrate 962. This disposition of shutter plate 952 aattenuates an optical beam that passes through the opening in thesubstrate 962.

In operation and use, microactuator 954 is electrically controlled bycontroller 561 to drive shuttle 990 in a forward direction (a downwarddirection in FIG. 13) from its rest position shown in FIG. 13 to itsactuated position shown in FIG. 14. Such movement of shuttle pushesflexural member 1006 forward which in turn rotates lever 960 in acounterclockwise direction about pivot point 1004 so as to pull element952 in a rearward direction (an upward direction in FIG. 14) to a secondposition shown in FIG. 14. Similarly, microactuator 954 can beelectrically controlled by controller 561 to pull shuttle 990 in arearward direction (an upward direction in FIG. 13) from its restposition shown in FIG. 13 to a second position (not shown). Suchmovement of shuttle 990 pulls flexural member 1006 rearwardly which inturn rotates lever 960 in a clockwise direction about pivot point 1004so as to push optical element 952 in a forward direction to a secondposition. In both instances, bendable flexural member 1006 and pivotarms 1000 and 1002 accommodate the pivoting of lever 960 about pivotpoint 1004. The pivoting of lever 960 about pivot point 1004 in bothclockwise and counterclockwise directions allows optical element 952coupled to the second extremity 960 b of lever 960 to move in bothclockwise and counterclockwise directions. Stop 1006 is provided onsubstrate 962 to limit the maximum travel of lever 960. The precise andvariable control of motor 954 allows shutter plate 952 to dynamicallyattenuate the optical beam over the entire circular region of the beamor any predetermined portion of the beam.

The microdevice 950 of the present invention is suitable for use eitheras a variable optical attenuator or as an on-off shutter in an opticalcommunication system. As such the microdevice of the present inventionis advantageous over the prior art microdevices which have limitationsin ability to divert all or portion of the optical beam and issusceptible to external accelerations or vibrations. The microdevice ofthe present invention is substantially mechanically balanced and thusprovides the variable optical attenuator or shutter with substantialimmunity to undesirable externally applied forces. Further, by adjustingthe lever ratio of the device, the deflection of the device can becontrolled. In one embodiment of the invention, the lever of the deviceis pivotable about the pivot point through an angle of at least fivedegrees in both clockwise and counterclockwise directions and the lightblocking element or shutter plate is movable in the direction of travelthrough a distance of at least 200 microns in both clockwise andcounterclockwise directions. The ability of large deflections allows themicrodevice to be used in relatively large collimated, converging, ordiverging optical beams, which results in reduced insertion losscompared to prior art devices. This is particularly useful in a tunablelaser system employing an external cavity laser design where the outputbeam from such a system usually has a diameter of about 150 microns.Allowing for alignment tolerances, the output beam can be located in acircular region about 200 microns or more in diameter. To provide anattenuator for such a laser system, a shutter with a travel of at least200 microns is desirable. The microdevice of the present invention canprovide large structure deflections at least about 200 microns in bothclockwise and counterclockwise directions and is thus suitable for usein such tunable laser systems. The microdevice of the present inventioncan be scaled larger or smaller to any suitable size so as to provide alow cost solution for commercial applications.

The microdevice of the present invention are not limited for use intunable lasers, the telecommunications industry or optical apparatus, itbeing appreciated that the microdevice and microactuators disclosedherein can be used in a wide range of applications, in addition to thosediscussed herein, to move any suitable element or member. It should alsobe appreciated by those skilled in the art that it would be possible tomodify the size, shape, appearance and methods of manufacture of variouselements of the invention, or to include or exclude various elements,and stay within the scope and spirit of the present invention.

1. A microdevice comprising a substrate, a movable structure overlayingthe substrate, an element and a lever assembly having a pivot and alever coupled to and pivotable about the pivot, the lever having a firstextremity coupled to the movable structure and an opposite secondextremity coupled to the element whereby the movable structure causesthe lever to pivot about the pivot so as to move the element in adirection of travel and the element is substantially counterbalancedrelative to the movable structure to inhibit undesirable movement of theelement in the direction of travel in response to externally appliedforces.
 2. The microdevice of claim 1 wherein the pivot has an X-shapeconfiguration and is formed from bendable first and second pivot arms,each of the first and second pivot arms having a first end portioncoupled to the substrate and a second end portion coupled to the lever,the first and second pivot arms having respective central portions thatare coupled together to form a pivot about which the lever pivots. 3.The microdevice of claim 2 wherein the lever has a first length from thefirst extremity to the pivot point and a second length from the secondextremity to the pivot point, the ratio of the second length to thefirst length ranging from two to three.
 4. The microdevice of claim 1further comprising an elongated flexural member for coupling the movablestructure to the first extremity of the lever.
 5. The microdevice ofclaim 1 wherein the movable structure includes a comb drive member. 6.The microdevice of claim 5 wherein the comb drive member is a linearcomb drive member.
 7. The microdevice of claim 1 wherein the element isan optical element.
 8. The microdevice of claim 7 wherein the opticalelement is a light blocking member.
 9. The microdevice of claim 1wherein the element pivots about a pivot axis extending perpendicular tothe substrate.
 10. The microdevice of claim 1 wherein the element movesin a plane parallel to the plane of the movable structure.
 11. Amicrodevice for use with a laser providing an optical beam comprising asubstrate, a light-blocking element, a drive member overlying thesubstrate and a lever assembly having a pivot and a lever coupled to andpivotable about the pivot, the lever having a first extremity coupled tothe drive member and an opposite second extremity coupled to thelight-blocking element whereby the drive member causes the lever topivot about the pivot so as to move the light-blocking element in adirection of travel to block at least a portion of the optical beam anda counterbalance coupled to the light-blocking member for inhibitingundesirable movement of the light-blocking element in the direction oftravel in response to externally applied forces.
 12. The microdevice ofclaim 11 wherein the pivot is X-shaped.
 13. The microdevice of claim 11wherein the drive member is a comb drive member.
 14. The microdevice ofclaim 11 wherein the drive member is an electrically-driven drivemember.
 15. The microdevice of claim 11 wherein the lever pivots about apivot axis extending perpendicular to the substrate.
 16. A microdevicecomprising a substrate extending in a first plane, a movable element, amicroelectromechanical drive member overlying the substrate, a leverassembly having a pivot and a lever coupled to and pivotable about thepivot in a second plane extending substantially parallel to the firstplane, the lever having a first extremity coupled to the drive memberand a second extremity coupled to the element whereby the drive membercauses the lever to pivot about the pivot so as to move the element in adirection of travel, and a counterbalance coupled to the element forinhibiting undesirable movement of the element in a direction of travelin response to externally applied forces.
 17. The microdevice of claim16 wherein the drive member is a comb drive member.
 18. The microdeviceof claim 1, wherein the substrate extends in a first plane and the leveris pivotable about the pivot in a second plane extending substantiallyparallel to the first plane.
 19. A microdevice comprising a substrate,first and second movable structures overlaying the substrate, and alever assembly having a pivot and a lever coupled to and pivotable aboutthe pivot, the lever having a first extremity coupled to the firstmovable structure and an opposite second extremity coupled to the secondmovable structure whereby the first movable structure causes the leverto pivot about the pivot so as to move the second movable structure in adirection of travel, the second movable structure being substantiallycounterbalanced relative to the first movable structure to inhibitundesirable movement of the first movable structure in the direction oftravel in response to externally applied forces.
 20. The microdevice ofclaim 19 wherein the first movable structure includes anelectrically-driven drive member.
 21. The microdevice of claim 19wherein the first movable structure includes a first electrically-drivendrive member and the second movable structure includes a secondelectrically-driven drive member.
 22. The microdevice of claim 19wherein the first movable structure includes a comb drive member. 23.The microdevice of claim 19 wherein the first movable structure includesa first comb drive member and the second movable structure includes asecond comb drive member.
 24. The microdevice of claim 19 wherein thefirst movable structure extends in a first plane and the second movablestructure moves in a second plane parallel to the first plane.